1. Field of the Invention
The present invention relates to a packaging film for use in fields of foods, medicines and the like, and a preparation method thereof.
2. Description of the Related Art
In general, a film with aluminum deposited thereon is widely used in a packaging material for packaging a food, a medicine or the like which needs to be prevented from being changed in properties due to humidity or oxygen, and from adsorbing different molecules.
However, since the aluminum deposited film is made opaque by the deposited aluminum, the film cannot be used in a case where contents requires to be seen from the outside, or in other cases. The film is disadvantageously limited in applications as the packaging material.
To solve the problem, there has also been suggested, as a transparent packaging material, another packaging film in which a plastic film is coated with an inorganic oxide such as silicon dioxide, but this inorganic oxide coated film is inferior to the aluminum deposited film in gas barrier properties for preventing the permeation of humidity, oxygen and the like. Furthermore, this kind of film is not suitable for performing the recycling of the packaging material which has been advanced recently, because the packaging material is contaminated with silicon dioxide.
Moreover, in a case where either of the aluminum deposited film and the inorganic oxide coated film is elongated by tensile force during its use, its gas barrier properties are disadvantageously remarkably deteriorated.
The present invention has been developed to solve the aforementioned problems of the conventional packaging film for packaging foods, medicines and the like.
That is to say, a first object of the invention is to provide a packaging film which has transparency, can prevent the adsorption of low-molecular organic compounds (aromatic components), has superiority in adhesion, alkali resistance and gas barrier properties, can be easily recycled and is not deteriorated in gas barrier properties even if elongation occurs on the film.
Furthermore, a second object of the invention is to provide a method of preparing the packaging film which can be performed without causing wrinkles or the like on the film.